According to the DOELP (s. v.), Cambedo is a derivative of the old feminine noun camba, with an obscure meaning, perhaps ‘grindstone, hand mill’. In any case, it could be a toponym with the Celtic component cam(b)- in allusion to a curved referent.

Cited bibliography: 

DOELP = Machado, José Pedro. Dicionário onomástico etimológico da língua portuguesa. Lisboa: Livros Horizonte, 2003, 3ª ed.